Rotator cuff tears are the most common cause of shoulder disability and pain accounting for 4.5 million physician visits and 75,000 surgeries annually. There is paucity of evidence addressing the diagnostic value of clinical history and physical examination of the shoulder. Consequently, magnetic resonance imaging (MRI) is used frequently to make a diagnosis of rotator cuff tear. Shoulder ultrasound is portable, office-based, and ~ 75% less expensive than MRI for diagnosis of rotator cuff tears. However, the diagnostic accuracy of ultrasound has not been established. This study will assess the sensitivity and specificity of a combination of select symptoms, physical examination findings, and ultrasound as compared to MRI and expert clinical diagnosis as a criterion standard. There is little evidence on the best treatment approach for rotator cuff tears and on factors associated with better outcomes of operative and non-operative treatment. There is no evidence from randomized clinical trials in this area. Current decision-making on non-operative treatment versus surgery is based largely on anecdotal clinical experience. Our study will determine predictors of pain and functional outcomes of non-operative and operative treatment of rotator cuff tears at two year follow-up period. Results from our study will provide evidence to inform clinical decision-making. This work will also lay a framework for a randomized controlled trial of surgery versus non-operative treatment which will be proposed in the final years of this award. The candidate's clinical background in Rehabilitation Medicine, and prior work in musculoskeletal diseases and patient-oriented studies is ideally suited for this mentored patient-oriented research program. His research and clinical environments at Brigham and Women's Hospital and Harvard Medical School offer him stimulating and rich learning opportunities. During the K23 award period, the candidate will obtain advanced training in research methodology, and shoulder disorders and imaging. The candidate will benefit from mentorship of Dr. Jeffrey N. Katz, a leading international expert in musculoskeletal diseases research. The candidate's mentoring team will also include Dr. Elena Losina, a biostatistician and independently funded R01 investigator, with extensive experience in mentoring of junior investigators; Dr. Laurence Higgins, an international clinical expert in shoulder disorders and Chief of Sports Medicine and Shoulder Surgery at Brigham and Women's Hospital, and; Dr. Joel Newman, a radiologist with expertise in shoulder ultrasound. The candidate with his prior training, research productivity, and clinical interests is uniquely situated to deliver the proposed research agenda and benefit from a highly qualified mentoring team.